Interesting post. I am enjoying a 3.5 gram cubensis journey at the moment, so bare with me if my post is off, lol.
I respect your admiration for the psilocybin mushroom, it's more of a mystical teacher than LSD. I actually have more experience with LSD than psilocybin, psilocin, and O-Acetylpsilocin, three tryptamines I find to be more mystical teachers and more expansive when it comes to soul and visions. LSD is still a favorite for me, I find it more introspective and the teachings it offers, for me, have been extreme insights into what my ego was, what it meant to lose it, what it meant to be reborn, extreme insights into reality and the way the mind works, insight into human psychology, and one could achieve an awesome head space with not much effort via meditation. There's nothing like your body being carried off by a guitar riff or violin and just riding the music into the endless head space your mind has to offer. After my 10th LSD trip or so I really started to learn how to use the compound for my best interest, and so many times I achieved ego loss and dissipated into eternity, not to mention the aesthetic nature of the compound is astoundingly beautiful when it comes to music and visuals.(at the 500ug to 1mg range)
If you love psilocybin and DMT, which I do, I think you should revisit LSD, maybe alone when you feel ready to. For some it's one of the most important of the tryptamines, and for others it's just another synthetic, but it sounds like you weren't getting great LSD if you classify the visuals as elementary, I've had visuals from LSD that have been on par in complexity with OEVs from DMT, and an amazing mix of colors bleeding together. Just thinking about the compound is inducing nostalgia in me, it's been about six months sense I actually had a decent LSD trip. The bulk of my LSD experiences have been trials started in my lonesome, and I make the choice to go be with people usually after I went to where I wanted to go and am back, the compound is beautiful for this. You can achieve ego loss and ego death an hour after taking a decent dose, melt into eternity for three hours, and still have five more hours to enjoy aesthetics and just enjoy existence, become a kid with an intellect's mind, retreat back to the basics, yet have the best perception in the room, this mindset is liberating. I'm not saying "GO TAKE LSD YOU BETTER LIKE IT." lol, I'm just saying you seem like an intelligent person and only after 6th LSD trials I say it's unfair to the compound and yourself to give it a rest already, there is more there than what you think. 
Sorry for that semi rant, I get passionate about my entheogens sometimes 
As for your interest in plant entheogens, don't ever stop researching, the reward is great. In regards to existence and space and time, have you ever heard of The Unified Field Theory? There's a lot of people who frown upon this theory, but I find it to be very interesting, and the bulk of it makes an incredible amount of sense. With the questions you say plague your mind, I figured this theory would at least spark a little interest into you.